JP2009177009A - Imaging apparatus and driving method of solid-state imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus capable of lowering the reading voltage of a solid-state imaging device. <P>SOLUTION: A digital camera, an example of the imaging apparatus, has a solid-state imaging device 5 containing a photoelectric conversion element 51 formed in a semiconductor substrate, a charge transfer channel 52a for transferring charges generated in the photoelectric conversion element 51 formed in the semiconductor substrate, and charge transfer electrodes V1-V6 formed above the charge transfer channel 52a through an insulation film 62. The digital camera has a reading electrode such that a charge transfer electrode V2 reads charge from the photoelectric conversion element 51 to the charge transfer channel 52a, a conductive light-shielding film 59 having an opening above the photoelectric conversion element 51 formed above the semiconductor substrate and the charge transfer electrodes V1-V6, and an imaging device driving part 10 for impressing a voltage, of which the polarity is inverted to that of reading pulse, to the light-shielding film 59 during the period for impressing the reading pulse to the reading electrode in the imaging period. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention includes a photoelectric conversion element formed in a semiconductor substrate, a charge transfer channel formed in the semiconductor substrate for transferring charges generated by the photoelectric conversion element, and an insulating film above the charge transfer channel. The present invention relates to an imaging apparatus having a solid-state imaging device including a formed charge transfer electrode.

  Conventionally, in a CCD (Charge Coupled Device) type solid-state imaging device, in order to realize low smear, low readout voltage, and low dark current, the light shielding film included in the solid-state imaging device has a positive charge readout period. A method of applying a voltage and applying a negative voltage during other periods has been proposed (see Patent Document 1).

  The CCD solid-state imaging device includes a photoelectric conversion element, a charge transfer channel that transfers charges generated by the photoelectric conversion element, and a charge transfer electrode formed above the charge transfer channel. Usually, a p-well layer is formed in an n-type silicon substrate, and an n-layer constituting a photodiode (PD) and an n-layer constituting a channel of a vertical charge transfer portion (VCCD) are formed on the surface of the p-well layer. Form.

The surface of the silicon substrate of the solid-state imaging device is usually a p-layer, except for the VCCD being an n-layer, for the following reasons (1) and (2). For this reason, the potential in the vicinity of the silicon substrate surface is normally kept at a constant potential (0 V).
(1) In the PD, it is necessary to cover the surface of the silicon substrate with a p layer in order to suppress dark current.
(2) Since the VCCD channel is an n-channel, it is necessary to form element isolation by a p-layer.

  Generally, the charge transfer electrode also serves as a readout electrode, and a positive voltage is applied to the charge transfer electrode other than the readout gate portion between the PD and the VCCD channel. At this time, the potential of the p-well layer, particularly the entire p-well layer on the surface of the silicon substrate (where the entire charge transfer electrode is covered) fluctuates to the positive side.

  Therefore, as disclosed in Patent Document 2, a voltage having a polarity opposite to the read voltage (hereinafter referred to as a cancellation pulse) is applied to the charge transfer electrode other than the read electrode at the time of charge read, and the potential of the p-well layer It is effective to keep the value constant.

  As described in Patent Document 1, the method of applying a positive voltage to the light shielding film at the time of reading has an effect of effectively increasing the gate length of the reading electrode and improving the potential modulation of the reading gate portion. However, since the light shielding film is also formed on other than the readout electrode (for example, the upper part of the PD of the light shielding film or the element isolation layer), by applying a positive voltage to the light shielding film, the p well layer, particularly the silicon substrate. The potential of the p-well layer on the surface is deepened to the plus side. Therefore, in the absence of the canceling pulse, a problem such as an increase in the depletion voltage occurs.

That is, when actually trying the technique of Patent Document 1, it is necessary to use a cancellation pulse in combination as described in Patent Document 2. However, for example, when a charge is read from the PD to the VCCD, a packet of the VCCD channel is formed between the charge transfer electrode forming the barrier of the VCCD channel and the readout electrode to which the readout pulse is applied. When a cancellation pulse is applied to a solid-state imaging device in which the number of charge transfer electrodes per PD and the number of driving phases of a VCCD are determined so that only one charge transfer electrode exists, the cancellation pulse is applied to the electrode adjacent to the readout electrode. Since it is always applied, there is a problem that a large potential difference is generated between the readout electrode and the adjacent electrode, and the reliability of the element is lowered. In addition, since the cancellation pulse is applied in the limited charge transfer electrode, there is a problem that the restriction on the timing design is large.
JP 2006-121112 A JP-A-7-322143

  The present invention has been made in view of the above circumstances, and provides an imaging measure capable of reducing the readout voltage of the solid-state imaging device without giving a canceling pulse to the charge transfer electrode of the solid-state imaging device at the time of readout. For the purpose. It is another object of the present invention to provide a method for driving an imaging apparatus that can improve the degree of freedom in timing design.

  An imaging apparatus according to the present invention includes a photoelectric conversion element formed in a semiconductor substrate, a charge transfer channel formed in the semiconductor substrate for transferring charges generated in the photoelectric conversion element, and an insulating film above the charge transfer channel An image pickup apparatus having a solid-state image pickup device including a charge transfer electrode formed via the read transfer electrode, wherein the charge transfer electrode is applied with a read pulse for reading charge from the photoelectric conversion device to the charge transfer channel An electrode, the solid-state imaging device is formed above the semiconductor substrate and the charge transfer electrode, includes a conductive light-shielding film having an opening above the photoelectric conversion device, and at least the readout pulse is applied to the readout electrode Voltage application means for applying a voltage having a polarity opposite to that of the readout pulse to the light shielding film during the application period is provided.

  In the imaging apparatus of the present invention, the voltage application unit applies a voltage having a polarity opposite to that of the readout pulse to the light shielding film during a period other than the period of applying the readout pulse.

  In the imaging apparatus according to the aspect of the invention, in a period other than the period in which the voltage application unit applies the readout pulse, a voltage whose absolute value is smaller than the voltage applied to the light shielding film in the period in which the readout pulse is applied. Apply to membrane.

  The image pickup apparatus according to the present invention includes a first voltage for forming a packet for accumulating charges in the charge transfer channel on the charge transfer electrode, and the barrier for forming a barrier between the packets in the charge transfer channel. A second voltage lower than the first voltage can be applied, and the voltage applied to the light shielding film during the period of applying the readout pulse is the same as the second voltage.

  In the imaging device of the present invention, the distance between the light shielding film and the charge transfer electrode is larger than the distance between two adjacent charge transfer electrodes.

  In the imaging device of the present invention, a film made of a material having a higher breakdown voltage than that between two adjacent charge transfer electrodes is included between the light shielding film and the charge transfer electrode.

  In the imaging device of the present invention, the material having a high breakdown voltage is silicon nitride.

  In the imaging device of the present invention, the light shielding film overlaps the photoelectric conversion element in a plan view.

  In the imaging device of the present invention, when the solid-state imaging device reads charges from the photoelectric conversion device to the charge transfer channel, a voltage is applied to form a barrier of a packet that accumulates charges in the charge transfer channel. Solid-state imaging having a configuration in which only one charge transfer electrode to which a voltage for forming the packet is applied exists between the charge transfer electrode to which the read pulse is applied It is an element.

  The solid-state imaging device driving method according to the present invention includes a photoelectric conversion element formed in a semiconductor substrate, a charge transfer channel formed in the semiconductor substrate for transferring charges generated in the photoelectric conversion element, and the charge transfer channel. A solid-state imaging device driving method comprising a charge transfer electrode formed above via an insulating film, wherein the charge transfer electrode applies a read pulse for reading charge from the photoelectric conversion device to the charge transfer channel The solid-state imaging element includes a conductive light-shielding film formed above the semiconductor substrate and the charge transfer electrode, and having an opening above the photoelectric conversion element, and at least the readout electrode includes the reading electrode. During the period of applying the readout pulse, a voltage having a polarity opposite to that of the readout pulse is applied to the light shielding film.

  In the solid-state imaging device driving method of the present invention, a voltage having a polarity opposite to that of the readout pulse is applied to the light-shielding film even during a period other than the period of applying the readout pulse.

  In the solid-state imaging device driving method according to the present invention, in a period other than the period in which the readout pulse is applied, a voltage having an absolute value smaller than the voltage applied to the light shielding film in the period in which the readout pulse is applied is applied to the light shielding film. Apply.

  In the solid-state imaging device driving method according to the present invention, a first voltage for forming a packet for accumulating charges in the charge transfer channel is formed on the charge transfer electrode, and a barrier between the packets is formed on the charge transfer channel. The voltage applied to the light shielding film during the period of applying the readout pulse is the same as the second voltage.

  In the solid-state imaging device driving method of the present invention, the distance between the light shielding film and the charge transfer electrode is larger than the distance between two adjacent charge transfer electrodes.

  In the solid-state imaging device driving method of the present invention, a film made of a material having a higher breakdown voltage than that between two adjacent charge transfer electrodes is included between the light shielding film and the charge transfer electrode.

  In the method for driving a solid-state imaging device according to the present invention, the material having a high withstand voltage is silicon nitride.

  In the solid-state imaging device driving method of the present invention, the light-shielding film overlaps the photoelectric conversion device in plan view.

  The solid-state imaging device driving method of the present invention is for forming a packet barrier that accumulates charges in the charge transfer channel when the solid-state imaging device reads charges from the photoelectric conversion device to the charge transfer channel. There is only one charge transfer electrode to which a voltage for forming the packet is applied between the charge transfer electrode to which a voltage is applied and the read electrode to which the read pulse is applied. It is a solid-state image sensor of composition.

  According to the present invention, an object of the present invention is to provide an imaging measure that can lower the readout voltage of a solid-state imaging device without giving a canceling pulse to the charge transfer electrode of the solid-state imaging device during readout. In addition, it is possible to provide a driving method of an imaging apparatus that can improve the degree of freedom in timing design.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram showing a schematic configuration of a digital camera which is an example of an imaging apparatus for explaining a first embodiment of the present invention.
The imaging system of the digital camera shown in the figure includes a photographic lens 1, a CCD type solid-state imaging device 5, a diaphragm 2 provided therebetween, an infrared cut filter 3, and an optical low-pass filter 4.

  A system control unit 11 that performs overall control of the electrical control system of the digital camera controls the flash light emitting unit 12 and the light receiving unit 13 and controls the lens driving unit 8 to adjust the position of the photographing lens 1 to the focus position and zoom. The exposure amount is adjusted by adjusting the aperture amount of the aperture 2 via the aperture drive unit 9.

  Further, the system control unit 11 drives the solid-state imaging device 5 via the imaging device driving unit 10 and outputs a subject image captured through the photographing lens 1 as a color signal. An instruction signal from the user is input to the system control unit 11 through the operation unit 14.

  The electric control system of the digital camera further includes an analog signal processing unit 6 that performs analog signal processing such as correlated double sampling processing connected to the output of the solid-state imaging device 5, and RGB output from the analog signal processing unit 6. And an A / D conversion circuit 7 for converting the color signals into digital signals, which are controlled by the system control unit 11.

  Furthermore, the electric control system of this digital camera generates image data by performing main memory 16, memory control unit 15 connected to main memory 16, interpolation calculation, gamma correction calculation, RGB / YC conversion processing, and the like. A digital signal processing unit 17, a compression / decompression processing unit 18 that compresses image data generated by the digital signal processing unit 17 into a JPEG format or decompresses compressed image data, and a digital signal processing unit 17 that integrates photometric data. The integration unit 19 for obtaining the gain of white balance correction performed by the camera, the external memory control unit 20 to which the removable recording medium 21 is connected, and the display control unit 22 to which the liquid crystal display unit 23 mounted on the back of the camera is connected. These are connected to each other by a control bus 24 and a data bus 25, and are controlled by commands from the system control unit 11. That.

FIG. 2 is a schematic plan view showing a configuration example of a solid-state imaging device mounted on the digital camera shown in FIG.
The solid-state imaging device shown in FIG. 2 has a large number of photoelectric conversion elements (for example, photodiodes) 51 arranged in a square lattice pattern in a vertical direction and a horizontal direction perpendicular thereto, and charges generated in each photoelectric conversion element 51 are vertically aligned. A plurality of vertical charge transfer units 52 that transfer in the direction, a horizontal charge transfer unit 53 that transfers the charges transferred through the plurality of vertical charge transfer units 52 in the horizontal direction, and a charge that has been transferred through the horizontal charge transfer unit 53 And an output unit 54 for outputting a signal corresponding to the above.

  The vertical charge transfer section 52 includes a charge transfer channel 52a (only part of which is shown) formed to extend in the vertical direction on the right side corresponding to the photoelectric conversion element array composed of the photoelectric conversion elements 51 arranged in the vertical direction, The charge transfer electrodes V1, V2, V3, V4, V5, and V6 are arranged in the vertical direction above the charge transfer channel 52a and can be independently applied with voltages.

  Charge readout for reading out the charge generated and accumulated in each photoelectric conversion element 51 to the charge transfer channel 52a between each photoelectric conversion element 51 of the photoelectric conversion element array and the corresponding charge transfer channel 52a. A portion 55 (shown schematically by an arrow in the figure) is formed.

  Among the photoelectric conversion element rows composed of the photoelectric conversion elements 51 arranged in the horizontal direction, the odd-numbered photoelectric conversion elements 51 are provided with three charge transfer electrodes V1 to V3 corresponding to the even-numbered photoelectric conversion elements 51. Three charge transfer electrodes V4 to V6 are provided correspondingly. The charge transfer electrodes V1 to V6 each have a low level (hereinafter referred to as VL; for example, −8V) transfer pulse for forming a packet for accumulating charges in the charge transfer channel 52a, and the packets transferred to the charge transfer channel 52a. A transfer pulse having a middle level (hereinafter referred to as VM; for example, 0 V) higher than VL for forming the barrier is applicable from the image sensor driving unit 10. Hereinafter, the charge transfer electrode to which the VL transfer pulse is applied is also referred to as a barrier electrode, and the charge transfer electrode to which the VM transfer pulse is applied is also referred to as a packet electrode.

  The charge transfer electrode V2 and the charge transfer electrode V5 also serve as a readout electrode for reading out charges from the photoelectric conversion element 51 to the charge transfer channel 52a, and also cover the charge readout portion 55 adjacent to the corresponding photoelectric conversion element 51. Has been. A high-level (hereinafter referred to as VH, for example, 12 to 13 V) read pulse higher than VM can also be applied to the charge transfer electrodes V2 and V5. By applying a read pulse to the read electrode, charge can be read from the photoelectric conversion element 51 to the charge transfer channel 52a.

  In the solid-state imaging device shown in FIG. 2, for example, in the first field, a read pulse is applied to the charge transfer electrode V2 while the charge transfer electrode V4 is a barrier electrode and the other charge transfer electrodes are packet electrodes. After reading out the charges from the odd-numbered photoelectric conversion elements 51, a six-phase transfer pulse is applied to the charge transfer electrodes V1 to V6 to transfer the charges. Next, in the second field, with the charge transfer electrode V1 as a barrier electrode and the other charge transfer electrode as a packet electrode, a read pulse is applied to the charge transfer electrode V5 to charge from the photoelectric conversion elements 51 in even rows. Then, a six-phase transfer pulse is applied to the charge transfer electrodes V1 to V6 to transfer this charge. With such an operation, charges can be read from all the photoelectric conversion elements 51.

FIG. 3 is a schematic plan view showing another configuration example of the solid-state imaging device mounted on the digital camera shown in FIG. In FIG. 3, the same components as those in FIG.
The solid-state imaging device shown in FIG. 3 has a configuration in which the vertical charge transfer unit 52 shown in FIG. 2 is changed to a vertical charge transfer unit 52 ′.

  The vertical charge transfer unit 52 ′ is composed of a charge transfer channel 52a and charge transfer electrodes V1, V2, V3, and V4 that are arranged in the vertical direction above the charge transfer channel 52a and that can independently apply a voltage. ing.

  The odd-numbered photoelectric conversion elements 51 are provided with two charge transfer electrodes V1 and V2, and the even-numbered photoelectric conversion elements 51 are provided with two charge transfer electrodes V3 and V4. A VL transfer pulse and a VM transfer pulse can be applied to the charge transfer electrodes V1 to V4 from the image sensor driving unit 10, respectively.

  The charge transfer electrode V1 and the charge transfer electrode V3 also serve as a readout electrode for reading out charges from the photoelectric conversion element 51 to the charge transfer channel 52a, and also cover the charge readout portion 55 adjacent to the corresponding photoelectric conversion element 51. Has been. A readout pulse can also be applied to the charge transfer electrodes V1, V3. By applying a read pulse to the read electrode, charge can be read from the photoelectric conversion element 51 to the charge transfer channel 52a.

  In the solid-state imaging device shown in FIG. 3, for example, in the first field, a read pulse is applied to the charge transfer electrode V1 while the charge transfer electrode V3 is a barrier electrode and the other charge transfer electrode is a packet electrode. After reading out the charges from the odd-numbered photoelectric conversion elements 51, a four-phase transfer pulse is applied to the charge transfer electrodes V1 to V4 to transfer the charges. Next, in the second field, with the charge transfer electrode V1 as a barrier electrode and the other charge transfer electrodes as packet electrodes, a read pulse is applied to the charge transfer electrode V3 to charge from the photoelectric conversion elements 51 in the even-numbered rows. Then, a four-phase transfer pulse is applied to the charge transfer electrodes V1 to V4 to transfer this charge. With such an operation, charges can be read from all the photoelectric conversion elements 51.

  The solid-state imaging device shown in FIG. 3 is a state in which a charge is transferred from the photoelectric conversion element 51 to the charge transfer channel 52a and a read transfer pulse is applied to the charge transfer electrode forming the barrier of the charge transfer channel 52a. The number of charge transfer electrodes per photoelectric conversion element (= 2) and the number of drive phases of the vertical charge transfer unit 52 ′ so that there is only one charge transfer electrode forming a packet between the electrodes. (= 4 phases) is determined. For this reason, if an attempt is made to apply a cancellation pulse, the cancellation pulse is applied next to the readout electrode, and there is a problem that the reliability of the element is lowered.

FIG. 4 is a schematic plan view showing another configuration example of the solid-state imaging device mounted on the digital camera shown in FIG.
The solid-state imaging device shown in FIG. 4 is configured such that even-numbered photoelectric conversion device rows are converted into odd-numbered photoelectric conversion devices among the photoelectric conversion device rows composed of the photoelectric conversion devices 51 arranged in the horizontal direction of the solid-state imaging device shown in FIG. The element rows are shifted in the horizontal direction by ½ of the arrangement pitch of the photoelectric conversion elements 51 of each photoelectric conversion element row. Further, since the positions of the photoelectric conversion elements 51 in the even-numbered photoelectric conversion element rows are shifted, the charge transfer channel 52a has a meandering shape extending in the vertical direction between the photoelectric conversion element columns so as to avoid the photoelectric conversion elements 51. .

  Charge transfer electrodes V1, V2, V3, and V4 are provided above the charge transfer channel 52a of the solid-state imaging device shown in FIG. The charge transfer electrodes V <b> 1 to V <b> 4 each have a meandering shape extending in the horizontal direction while avoiding each photoelectric conversion element 51 between the photoelectric conversion element rows. VL and VM transfer pulses can be applied to the charge transfer electrodes V1 to V4 by the image sensor driving unit 10, respectively.

  Each photoelectric conversion element in the odd-numbered photoelectric conversion element row corresponds to an electrode group in which charge transfer electrodes V3, V4, V1, and V2 are arranged in this order, and each photoelectric conversion element in the even-numbered photoelectric conversion element row has a charge. An electrode group in which the transfer electrodes V1, V2, V3, and V4 are arranged in this order corresponds.

  Charge readout for reading out the charge generated and accumulated in each photoelectric conversion element 51 to the charge transfer channel 52a between each photoelectric conversion element 51 of the photoelectric conversion element array and the corresponding charge transfer channel 52a. A portion 55 (only part of which is shown in the figure) is formed.

  The charge transfer electrode V1 and the charge transfer electrode V3 also serve as a readout electrode for reading out charges from the photoelectric conversion element 51 to the charge transfer channel 52a, and also cover the charge readout portion 55 adjacent to the corresponding photoelectric conversion element 51. Has been. A VH readout pulse can also be applied to the charge transfer electrodes V1, V3. By applying a read pulse to the read electrode, charge can be read from the photoelectric conversion element 51 to the charge transfer channel 52a.

  In the solid-state imaging device shown in FIG. 4, for example, first, in a state where the charge transfer electrode V3 is a barrier electrode and the other charge transfer electrodes are packet electrodes, a read pulse is applied to the charge transfer electrode V1 to generate odd-numbered rows. After the charge is read from the photoelectric conversion element 51, the charge transfer electrode V1 is used as a barrier electrode, and the other charge transfer electrode is used as a packet electrode. In this state, a read pulse is applied to the charge transfer electrode V3, The charge is read from 51. Thereafter, a four-phase transfer pulse is applied to the charge transfer electrodes V1 to V4 to transfer this charge. With such an operation, charges can be read from all the photoelectric conversion elements 51.

  The solid-state imaging device shown in FIG. 4 is a state in which a charge is transferred from the photoelectric conversion element 51 to the charge transfer channel 52a and a read transfer pulse is applied to the charge transfer electrode forming the barrier of the charge transfer channel 52a. The number of charge transfer electrodes per photoelectric conversion element (= 4) and the number of drive phases of the vertical charge transfer unit 52 ′ so that there is only one charge transfer electrode forming a packet between the electrodes. (= 4 phases) is determined. For this reason, when an attempt is made to apply a cancellation pulse, the cancellation pulse is applied next to the readout electrode, and there is a problem that the reliability of the element is lowered.

FIG. 5 is a schematic cross-sectional view taken along line AA of the solid-state imaging device shown in FIGS.
The photoelectric conversion element 51, the charge transfer channel 52a, and the charge reading unit 55 are each formed in a p-well layer 57 formed on an n-type silicon substrate. The n-type silicon substrate and the p well layer 57 constitute a semiconductor substrate.

  The photoelectric conversion element 51 includes an n-type impurity layer 51a formed on the inner side from the surface of the p-well layer 57, and a p-type impurity layer 51b formed on the inner side from the surface of the n-type impurity layer 51a for suppressing dark current. Has been.

  An element isolation layer 56 made of a p-type impurity layer is formed between the photoelectric conversion element 51 and the charge transfer channel 52a not corresponding to the photoelectric conversion element 51.

  The charge transfer channel 52a is constituted by an n-type impurity layer formed inside from the surface of the p-well layer 57. The charge reading unit 55 is formed by a region of the p-well layer 57 between the photoelectric conversion element 51 and the charge transfer channel 52a.

  The charge transfer electrode V2 is formed so as to cover not only the charge transfer channel 52a but also the upper part of the charge reading portion 55. The charge transfer electrode V2 is formed on the gate insulating film 62 formed on the p-well layer 57. On the charge transfer electrode V2 and the gate insulating film 62, an insulating film 58 for insulating the charge transfer electrode V2 from the adjacent charge transfer electrode is formed.

  A light shielding film 59 made of tungsten or the like having conductivity and light shielding properties is formed on the insulating film 58. The light shielding film 59 has an opening above the photoelectric conversion element 51, and the light receiving range of the photoelectric conversion element 51 is defined by the opening area. The opening of the light shielding film 59 is formed inside the photoelectric conversion element 51 in a plan view, and the light shielding film 59 has a portion that overlaps the photoelectric conversion element 51 in a plan view. In addition, a wiring (not shown) is connected to the light shielding film 59, and a predetermined voltage can be applied to the wiring from the image sensor driving unit 10.

  The solid-state imaging device mounted on the digital camera shown in FIG. 1 may be any CCD type solid-state imaging device having a light shielding film, and is not limited to that shown in FIGS.

Hereinafter, the operation at the time of imaging of the digital camera will be described.
FIG. 6 is a timing chart for explaining a method of driving the solid-state imaging device shown in FIG. FIG. 7 is a timing chart for explaining a method of driving the solid-state imaging device shown in FIG. FIG. 8 is a timing chart for explaining a method of driving the solid-state imaging device shown in FIG.

(Driving example of solid-state imaging device shown in FIG. 2)
As shown in FIG. 6, first, in the first field, the charge transfer electrode V4 is used as a barrier electrode, the other charge transfer electrodes are used as packet electrodes, and a VM pulse is applied to the light shielding film 59 before charge reading. In this state, a read pulse is applied to the charge transfer electrode V2 to read charges from the odd-numbered photoelectric conversion elements 51. During the period in which the readout pulse is applied to the charge transfer electrode V2, a VL pulse is applied to the light shielding film 59. After the completion of charge reading, a six-phase transfer pulse is applied to the charge transfer electrodes V1 to V6 to transfer the read charge.

Next, in the second field, before charge reading, the charge transfer electrode V1 is used as a barrier electrode, the other charge transfer electrodes are used as packet electrodes, and a VM pulse is applied to the light shielding film 59. In this state, a read pulse is applied to the charge transfer electrode V5 to read out charges from the even number of photoelectric conversion elements 51. During the period in which the readout pulse is applied to the charge transfer electrode V5, a VL pulse is applied to the light shielding film 59. After the completion of charge reading, a six-phase transfer pulse is applied to the charge transfer electrodes V1 to V6 to transfer the read charge.
The imaging element driving unit 10 continues to apply the VM pulse to the light shielding film 59 during the period in which the solid-state imaging element 5 is operating, excluding the period in which the readout pulse is applied to the readout electrode.

  In this way, by applying a voltage having a polarity opposite to that of the readout pulse to the light shielding film 59 during the period in which the readout pulse is applied to the readout electrode, the potential of the p-well layer 57, particularly the surface thereof, is stabilized. It is possible to read out charges and suppress an increase in depletion voltage. Since the potential of the p-well layer 57 is stabilized, it is not necessary to apply a cancel pulse having a polarity opposite to that of the read pulse to any of the charge transfer electrodes that are packet electrodes at the time of charge reading. The saturation capacity of the vertical charge transfer unit 52 can be increased without reducing the number by one.

(Driving example of solid-state imaging device shown in FIG. 3)
As shown in FIG. 7, first, in the first field, the charge transfer electrode V3 is used as a barrier electrode, the other charge transfer electrodes are used as packet electrodes, and a VM pulse is applied to the light shielding film 59 before charge reading. In this state, a read pulse is applied to the charge transfer electrode V <b> 1 to read charges from the odd-numbered photoelectric conversion elements 51. During the period in which the readout pulse is applied to the charge transfer electrode V1, a VL pulse is applied to the light shielding film 59. After the completion of the charge reading, a four-phase transfer pulse is applied to the charge transfer electrodes V1 to V4 to transfer the read charge.

Next, in the second field, before charge reading, the charge transfer electrode V1 is used as a barrier electrode, the other charge transfer electrodes are used as packet electrodes, and a VM pulse is applied to the light shielding film 59. In this state, a read pulse is applied to the charge transfer electrode V3 to read charges from the even number of photoelectric conversion elements 51. During the period in which the read pulse is applied to the charge transfer electrode V3, a VL pulse is applied to the light shielding film 59. After the completion of the charge reading, a four-phase transfer pulse is applied to the charge transfer electrodes V1 to V4 to transfer the read charge.
The imaging element driving unit 10 continues to apply the VM pulse to the light shielding film 59 during the period in which the solid-state imaging element 5 is operating, excluding the period in which the readout pulse is applied to the readout electrode.

  In this way, by applying a voltage having a polarity opposite to that of the readout pulse to the light shielding film 59 during the period in which the readout pulse is applied to the readout electrode, the potential of the p-well layer 57, particularly the surface thereof, is stabilized. It is possible to read out charges and suppress an increase in depletion voltage. Since the potential of the p-well layer 57 is stabilized, it is not necessary to apply a cancel pulse having a polarity opposite to that of the read pulse to any of the charge transfer electrodes that are packet electrodes at the time of charge reading. The saturation capacity of the vertical charge transfer unit 52 can be increased without reducing the number by one.

  Further, when the cancellation pulse method is employed in the solid-state imaging device having the configuration shown in FIG. 3, the cancellation pulse is always applied to the charge transfer electrode adjacent to the readout electrode. In this way, when a cancellation pulse is applied to the charge transfer electrode adjacent to the readout electrode, the potential difference between the readout electrode and the adjacent charge transfer electrode increases, and breakdown, dielectric breakdown between the charge transfer electrodes, This causes problems such as a decrease in reliability (depletion voltage deterioration due to continuous driving, transfer efficiency deterioration over time, etc.). For this reason, in the solid-state imaging device having the configuration as shown in FIG. 3, it is not particularly preferable to employ the cancellation pulse method. Therefore, it is particularly effective to employ the above-described driving that controls the voltage applied to the light shielding film 59.

(Driving example of solid-state imaging device shown in FIG. 4)
As shown in FIG. 8, first, before charge reading, the charge transfer electrode V3 is used as a barrier electrode, the other charge transfer electrodes are used as packet electrodes, and a VM pulse is applied to the light shielding film 59. In this state, a read pulse is applied to the charge transfer electrode V <b> 1 to read charges from the odd-numbered photoelectric conversion elements 51. During the period in which the readout pulse is applied to the charge transfer electrode V1, a VL pulse is applied to the light shielding film 59.

  After reading out the charges from the odd-numbered photoelectric conversion elements 51, the charge transfer electrode V1 is used as a barrier electrode, the other charge transfer electrodes are used as packet electrodes, and a VM pulse is applied to the light shielding film 59. In this state, a read pulse is applied to the charge transfer electrode V3 to read charges from the even number of photoelectric conversion elements 51. During the period in which the read pulse is applied to the charge transfer electrode V3, a VL pulse is applied to the light shielding film 59. After the completion of the charge reading, a four-phase transfer pulse is applied to the charge transfer electrodes V1 to V4 to transfer the read charge.

  In this way, by applying a voltage having a polarity opposite to that of the readout pulse to the light shielding film 59 during the period in which the readout pulse is applied to the readout electrode, the potential of the p-well layer 57, particularly the surface thereof, is stabilized. It is possible to read out charges and suppress an increase in depletion voltage. Since the potential of the p-well layer 57 is stabilized, it is not necessary to apply a cancel pulse having a polarity opposite to that of the read pulse to any of the charge transfer electrodes that are packet electrodes at the time of charge reading. The saturation capacity of the vertical charge transfer unit 52 can be increased without reducing the number by one.

  Further, when the cancellation pulse method is adopted in the solid-state imaging device having the configuration shown in FIG. 4, the cancellation pulse is always applied to the charge transfer electrode adjacent to the readout electrode (FIG. 8). The broken line shown is the waveform when the cancellation pulse is applied). In this way, when a cancellation pulse is applied to the charge transfer electrode adjacent to the readout electrode, the potential difference between the readout electrode and the adjacent charge transfer electrode increases, and breakdown, dielectric breakdown between the charge transfer electrodes, This causes problems such as a decrease in reliability (depletion voltage deterioration due to continuous driving, transfer efficiency deterioration over time, etc.). For this reason, in the solid-state imaging device having the configuration as shown in FIG. Therefore, it is particularly effective to employ the above-described driving that controls the voltage applied to the light shielding film 59.

  In the above description, it is assumed that a pulse having a polarity opposite to that of the readout pulse is applied to the light shielding film 59 only during a period in which the readout pulse is applied to the readout electrode during the period in which the solid-state imaging device 5 is operating. However, a pulse having a polarity opposite to that of the readout pulse may be applied to the light shielding film 59 in a period other than this period. In other words, during the period when the solid-state imaging device 5 is operating, a pulse having a polarity opposite to that of the readout pulse (for example, a pulse of VL) may be continuously applied to the light shielding film 59. By doing so, smear and dark current can be reduced.

  As described above, when a pulse having a polarity opposite to that of the readout pulse is continuously applied to the light shielding film 59, the absolute value of the pulse applied to the light shielding film 59 during a period other than the period during which the readout pulse is applied is read out. It is preferable that the absolute value of the pulse applied to the light shielding film 59 during the period in which the pulse is applied is smaller (for example, −2, 3 V). By doing so, power consumption can be kept low and smear during standby can be reduced.

  In the above description, the pulse applied to the light shielding film 59 during the period in which the readout pulse is applied is a VL pulse. However, this pulse may be a pulse having a polarity opposite to that of the readout pulse. Any value is acceptable. For example, -2V or -3V may be used. As described above, by making the pulse applied to the light shielding film 59 a VL pulse, the driver that generates the pulse applied to the light shielding film 59 and the driver that generates the pulse applied to the charge transfer electrode are shared. Cost reduction.

  In the above description, the read pulse and the VL pulse are simultaneously applied to the light shielding film 59. However, at the rising or falling of the VL pulse applied to the light shielding film 59, the VL pulse is applied. It may be applied with a time difference from the readout pulse. By doing so, it is possible to prevent an electric field from being suddenly applied between the light shielding film 59 and the charge transfer electrode. In the case of the solid-state imaging device shown in FIG. 4, as shown in parentheses in FIG. 8, the period from the start of applying the read pulse to the charge transfer electrode V1 to the end of applying the read pulse to the charge transfer electrode V3. The VL pulse may be continuously applied to the light shielding film 59.

  Further, as shown in FIG. 5, since the light shielding film 59 also covers the element isolation layer 56, by performing the above-described driving, blooming between adjacent vertical charge transfer units 52 and charge reading are performed. An effect of suppressing blooming is also obtained.

(Second embodiment)
FIG. 9 is a diagram showing a modification of the solid-state imaging device shown in FIG.
The solid-state imaging device shown in FIG. 9 has a configuration in which an antireflection film 61 made of silicon nitride (SiN) or the like is embedded in the insulating film 58 of the solid-state imaging device shown in FIG. The antireflection film 61 is provided with an opening for passing hydrogen in a sintering process, which is a manufacturing process of a solid-state imaging device.

  By providing the antireflection film 61, irregular reflection of incident light on the surface of the photoelectric conversion element 51 can be suppressed, so that sensitivity can be improved.

  Although not shown in FIG. 9, another charge transfer electrode is provided adjacent to the charge transfer electrode V2, and these are insulated by an interelectrode insulating film such as silicon oxide. In addition, the inter-electrode insulating film and the antireflection film 61 exist between each charge transfer electrode and the light shielding film 59. For this reason, the distance between the light shielding film 59 and each charge transfer electrode is larger than the distance between two adjacent charge transfer electrodes. By providing the antireflection film 61, the distance between the light shielding film 59 and the charge transfer electrodes is increased. Can be higher than the voltage between the charge transfer electrodes. In addition, since silicon nitride has a much higher breakdown voltage than silicon oxide, for this reason, the breakdown voltage between the light shielding film 59 and the charge transfer electrode can be higher than the breakdown voltage between the charge transfer electrodes. .

The figure which shows schematic structure of the digital camera which is an example of the imaging device for demonstrating 1st embodiment of this invention. FIG. 1 is a schematic plan view showing a configuration example of a solid-state imaging device mounted on the digital camera shown in FIG. The plane schematic diagram which shows another structural example of the solid-state image sensor mounted in the digital camera shown in FIG. The plane schematic diagram which shows another structural example of the solid-state image sensor mounted in the digital camera shown in FIG. A cross-sectional schematic view taken along line AA in FIGS. 2, 3, and 4. The figure which shows the drive timing chart of the solid-state image sensor shown in FIG. The figure which shows the drive timing chart of the solid-state image sensor shown in FIG. The figure which shows the drive timing chart of the solid-state image sensor shown in FIG. The figure which shows the modification (2nd embodiment) of the solid-state image sensor shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 5 Solid-state image sensor 10 Image sensor drive part 51 Photoelectric conversion element 52 Charge transfer channel 59 Light-shielding film 62 Insulating film V1-V3 Charge transfer electrode

Claims (18)

A photoelectric conversion element formed in a semiconductor substrate, a charge transfer channel formed in the semiconductor substrate for transferring charges generated by the photoelectric conversion element, and a charge formed above the charge transfer channel via an insulating film An imaging apparatus having a solid-state imaging device including a transfer electrode,
The charge transfer electrode includes a read electrode to which a read pulse for reading charge from the photoelectric conversion element to the charge transfer channel is applied;
The solid-state imaging device includes a conductive light-shielding film formed above the semiconductor substrate and the charge transfer electrode and having an opening above the photoelectric conversion device;
An imaging apparatus comprising: a voltage applying unit that applies a voltage having a polarity opposite to that of the readout pulse to the light shielding film during a period in which the readout pulse is applied to at least the readout electrode. The imaging apparatus according to claim 1,
The imaging apparatus in which the voltage applying unit applies a voltage having a polarity opposite to that of the readout pulse to the light shielding film during a period other than the period of applying the readout pulse. The imaging apparatus according to claim 2,
The imaging apparatus in which the voltage application unit applies a voltage having a smaller absolute value to the light shielding film than a voltage applied to the light shielding film during a period during which the readout pulse is applied during a period other than the period during which the readout pulse is applied. The imaging apparatus according to any one of claims 1 to 3,
The charge transfer electrode has a first voltage for forming a packet for accumulating charges in the charge transfer channel and lower than the first voltage for forming a barrier between the packets in the charge transfer channel. A second voltage can be applied,
An imaging apparatus in which a voltage applied to the light shielding film during the period of applying the readout pulse is the same as the second voltage. The imaging apparatus according to any one of claims 1 to 4,
An imaging apparatus in which a distance between the light shielding film and the charge transfer electrode is larger than a distance between two adjacent charge transfer electrodes. The imaging apparatus according to claim 5, wherein
An imaging device in which a film having a higher withstand voltage than that between two adjacent charge transfer electrodes is included between the light shielding film and the charge transfer electrode. The imaging apparatus according to claim 6,
An imaging device in which the material having a high breakdown voltage is silicon nitride. The imaging device according to any one of claims 1 to 7,
An imaging apparatus in which the light shielding film has an overlap with the photoelectric conversion element in plan view. The imaging apparatus according to any one of claims 1 to 8,
The charge transfer electrode to which a voltage for forming a barrier of a packet for accumulating charge in the charge transfer channel is applied when the solid-state imaging device reads out charge from the photoelectric conversion device to the charge transfer channel; An imaging apparatus, which is a solid-state imaging device having a configuration in which only one charge transfer electrode to which a voltage for forming the packet is applied exists between the readout electrode to which the readout pulse is applied. A photoelectric conversion element formed in a semiconductor substrate, a charge transfer channel formed in the semiconductor substrate for transferring charges generated by the photoelectric conversion element, and a charge formed above the charge transfer channel via an insulating film A solid-state imaging device driving method including a transfer electrode,
The charge transfer electrode includes a read electrode to which a read pulse for reading charge from the photoelectric conversion element to the charge transfer channel is applied;
The solid-state imaging device includes a conductive light-shielding film formed above the semiconductor substrate and the charge transfer electrode and having an opening above the photoelectric conversion device;
A method for driving a solid-state imaging device, wherein a voltage having a polarity opposite to that of the readout pulse is applied to the light shielding film at least during a period in which the readout pulse is applied to the readout electrode. A method for driving a solid-state imaging device according to claim 10,
A method for driving a solid-state imaging device, wherein a voltage having a polarity opposite to that of the readout pulse is applied to the light shielding film during a period other than the period during which the readout pulse is applied. It is a drive method of the solid-state image sensing device according to claim 11,
A method for driving a solid-state imaging element, wherein a voltage having an absolute value smaller than a voltage applied to the light-shielding film is applied to the light-shielding film during a period other than the period during which the readout pulse is applied. A method for driving a solid-state imaging device according to any one of claims 10 to 12,
A first voltage for forming a packet for accumulating charges in the charge transfer channel and a second voltage for forming a barrier between the packets in the charge transfer channel can be applied to the charge transfer electrode. And
A solid-state imaging device driving method, wherein a voltage applied to the light-shielding film during the period of applying the readout pulse is the same as the second voltage. It is a drive method of the solid-state image sensing device according to any one of claims 10 to 13,
A method for driving a solid-state imaging device, wherein a distance between the light shielding film and the charge transfer electrode is larger than a distance between two adjacent charge transfer electrodes. The solid-state imaging device driving method according to claim 14,
A method for driving a solid-state imaging device, wherein a film of a material having a higher withstand voltage is included between the light shielding film and the charge transfer electrode than between the two adjacent charge transfer electrodes. A method for driving a solid-state imaging device according to claim 15,
A method for driving a solid-state imaging device, wherein the material having a high breakdown voltage is silicon nitride. A driving method of a solid-state imaging device according to any one of claims 10 to 16,
A method for driving a solid-state imaging element, wherein the light-shielding film overlaps the photoelectric conversion element in plan view. A method for driving a solid-state imaging device according to any one of claims 10 to 17,
The charge transfer electrode to which a voltage for forming a barrier of a packet for accumulating charge in the charge transfer channel is applied when the solid-state imaging device reads out charge from the photoelectric conversion device to the charge transfer channel; A solid-state imaging device, which is a solid-state imaging device having a configuration in which only one charge transfer electrode to which a voltage for forming the packet is applied exists between the readout electrode to which the readout pulse is applied. Driving method.

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